Much of what we know regarding variations in Earth's climate during the past millennium comes from tree rings. But tree rings, like other proxies, attenuate some climate signals but amplify others, and their fidelity at longer timescales is difficult to gage. Even though dendroclimatology is well-established, questions remain about the climate clues encoded in tree rings — particularly at decadal-to-centennial timescales.
Labelling Requirements and Label Claims for Dietary Supplements and Recommend...
How long do trees remember?
1. HOW LONG DO TREES REMEMBER?
Climate Variability Across Scales Working Group | PAGES (Past Global Changes) | August 13, 2020
2. MUCH OF WHAT WE KNOW REGARDING VARIATIONS IN EARTH'S
CLIMATE DURING THE PAST MILLENNIUM COMES FROM TREE RINGS.
TREE RINGS, LIKE OTHER PROXIES, ATTENUATE SOME CLIMATE
SIGNALS BUT AMPLIFY OTHERS, AND THEIR FIDELITY AT LONGER
TIMESCALES IS DIFFICULT TO GAGE.
DENDROCLIMATOLOGY IS WELL-ESTABLISHED BUT QUESTIONS
REMAIN ABOUT THE CLIMATE CLUES ENCODED IN TREE RINGS —
PARTICULARLY AT DECADAL-TO-CENTENNIAL TIMESCALES.
3.
4.
5. MUCH OF WHAT WE KNOW
REGARDING VARIATIONS
IN EARTH'S CLIMATE
DURING THE PAST MILLENNIUM
COMES FROM TREE RINGS.
8. Source: Emile-Geay et al., Scientific Data (2017)
IN 2017, THE PAGES 2K INITIATIVE RELEASED A GLOBAL, COMMUNITY-SOURCED DATABASE OF
TEMPERATURE-SENSITIVE PROXIES SPANNING THE PAST TWO MILLENNIA.
12. Source: Hurst, Hydrological Sciences Journal (1956)
TREE-RING WIDTHS WERE AMONG THE INITIAL TYPES OF EVIDENCE USED BY HURST TO DESCRIBE
LONG-RANGE PERSISTENCE IN HYDROLOGICAL AND GEOPHYSICAL TIME SERIES.
14. Source: Lovejoy and Schertzer, Geophysical Research Le ers (2012)
BETWEEN 1 AND 500 YR, THEIR STOCHASTIC ESTIMATE OF CLIMATE SENSITIVITY
LEANS HEAVILY ON RECONSTRUCTIONS DERIVED MAINLY FROM TREE RINGS.
21. Tree age
Ring width
AS TREES GROW LARGER WITH AGE, THEY ARE OBLIGED TO FORM NEW WOOD
ABOUT THE EVER-INCREASING CIRCUMFERENCE OF THEIR BOLE.
22. Source: Björkland et al., New Phytologist (2017)
MAXIMUM LATEWOOD DENSITY INCREASES AS TREES TRANSITION FROM JUVENILE TO MATURE
WOOD, BUT LATER DECREASES AS FEWER RESOURCES ARE USED TO THICKEN CELL WALLS.
24. TRADITIONAL TREE-RING STANDARDIZATION METHODS
WOULD SEEM TO
PLACE A FUNDAMENTAL LIMIT
ON THE RESOLVABILITY OF
VERY LOW-FREQUENCY CLIMATE FLUCTUATIONS
FROM TREE RINGS
WHEN CLIMATE CHANGES MORE SLOWLY
THAN THE TYPICAL LIFESPAN
OF THE TREES BEING STUDIED.
“ ”
Ed Cook et al., 1995
The Holocene
26. Source: Klippel et al., Climate of the Past (2020)
COMPOSITES OF MARINE SEDIMENTS (ORANGE), LAKE SEDIMENTS (RED), AND GLACIAL ICE CORES
(BLUE) HAVE STRONG PRE-INDUSTRIAL COOLING TRENDS. BUT TREE RINGS (GREEN) DON’T!
31. Source: Coulthard et al., Quaternary Science Reviews (2020)
TREE-RING SEQUENCES USUALLY EXHIBIT HIGH PERSISTENCE OVER SEVERAL YEARS DUE TO
BIOLOGY (ARISING FROM CARBOHYDRATE STORAGE OR NEEDLE RETENTION) OR CLIMATE (DRIVEN
BY LAGS IN TEMPERATURE OR HYDROLOGY).
35. Source: Huybers et al.,Climate Dynamics (2015)
EVEN IF THE CLIMATIC ‘INPUTS’ TO A CLOSED BASIN HAVE LITTLE OR NO PERSISTENCE,
LAKE LEVELS WILL EXHIBIT STRONG LONG-TERM MEMORY
DUE TO HYDROLOGICAL STORAGE.
36.
37. IN PRINCIPLE,
PROXY AND GCM DATA
SHOULD YIELD A CONSISTENT VIEW
OF THE CLIMATE SYSTEM
ON [DECADAL AND LONGER] TIMESCALES.
IN PRACTICE…
“ ”
Toby Ault
CLIVAR Exchanges/Past Global Changes Magazine, 2017
38. Source: Chase et al., Elements (2018)
THE ELDERFIELD CURVE OF HOW CONFIDENCE IN A GIVEN PROXY EVOLVES OVER TIME
old-fashioned
phase?
39. DENDROCLIMATOLOGY IS WELL-
ESTABLISHED BUT QUESTIONS
REMAIN ABOUT THE CLIMATE
CLUES ENCODED IN TREE RINGS
— PARTICULARLY AT DECADAL-
TO-CENTENNIAL TIMESCALES.
41. EVERYTHING IS RELATED
TO EVERYTHING ELSE,
BUT NEAR THINGS
ARE MORE RELATED
THAN DISTANT THINGS.
“ ”
Waldo Tobler
University of California, Santa Barbara
42. Widespread drought caused narrow rings
to form across the southwest USA
during 1748 and 1750.
Source: Kurt Kipfmueller, University of Minnesota
43. HOW DOES THE AGREEMENT
BETWEEN TREE-RING RECORDS
AT DECADAL FREQUENCIES
AND LONGER
VARY ACROSS SPACE AND TIME?
and what is a reasonable expectation
(null hypothesis) for that behavior?
46. Signal-free detrending can
make tree-ring chronologies
more coherent with their
neighbors (➡), but in other
cases, it appears to introduce
low-frequency noise ( ).
Source: McPartland et al., Dendrochronologia (revision submi ed)
➡ ➡
47. IS IT POSSIBLE
TO IDENTIFY AN OPTIMAL DETRENDING
FOR THE RECOVERY OF
LOW-FREQUENCY PATTERNS
FROM TREE-RING NETWORKS OF VARIOUS
SIZES AND COMPOSITIONS?
and is it a good idea to do that?
49. …ONE MAY MODEL
THE FORMATION OF THE RECORD
BY EXPLICITLY REPRESENTING
THE CHAIN OF PHYSICAL AND BIOLOGICAL PROCESSES
WHICH LIE BETWEEN
THE CLIMATIC INFORMATION
AND THE OBSERVED SIGNAL.
“ ”
Joël Guiot
Past Global Changes Magazine, 2017
51. Source: Dee et al., Earth and Planetary Science Le ers (2017)
THE SPECTRA OF SYNTHETIC TREE-RING WIDTHS GENERATED BY PROCESS MODELS (GREEN LINE,
GRAY ERROR ESTIMATES) GENERALLY MATCH THE BEHAVIOR OF THE REAL DATA (BLACK LINE).
52. CAN WE USE PROCESS MODELS
TO CONSTRAIN
THE UPPER OR LOWER LIMITS OF
DECADAL-TO-CENTENNIAL
CLIMATE VARIABILITY
DURING THE PAST TWO MILLENNIUM?